1. Field of the Invention
This invention broadly concerns a vibrating screed used in compacting and smoothing flowable cementatious materials. More particularly, it is concerned with a vibrating screed which provides for improved and adjustable control by the operator over the relative vertical compacting and horizontal screeding forces applied to the material.
2. Description of the Prior Art
Various tools for working cementatious material into a finished shape for hardening are well known in the art. Such cementatious material is most commonly concrete which includes crushed rock or gravel as an aggregate. In finishing surfaces such as roads, walkways, foundations and the like, it is often desirable to both compact the mortar around the aggregate to consolidate and thereby densify the concrete, as well as smooth the upper surface to present a finished appearance.
In addition to trowels, smoothers and bull floats, powered screeds have been developed which aid in working the flowable concrete or other cementations material. These various devices include screeds powered by an electric motor, internal combustion engine or a pneumatic oscillator which are pushed or driven across the surface of the material to compact and smooth the material to a finished surface. Examples of such screeds are shown, for example, in my U.S. Pat. Nos. 4,591,291, 4,340,351 and 4,752,156.
As shown in my U.S. Pat. No. 4,591,291 referenced above and in U.S. Pat. No. 5,244,305, portable screeds which may be operated by a single operator and moved along the surface of the wet concrete are useful in finishing small to medium sized concrete pours. These screeds advantageously smooth and finish the surface using lightweight motors or engines which rotate use an eccentric to impart oscillating motion and thereby provide a finished surface. However, such devices have operating limitations which have given rise to the need for an improved portable screed. For example, the forces imparted by the eccentric on these existing portable screeds may cause accelerated wear on the bearing surfaces, may lack the ability to select a setting for imparting different amounts of compaction and smoothing, or may be incapable of providing both compaction and horizontal smoothing functions.
Accordingly, there has developed a need for an improved vibrating screed which can be easily transported and positioned by a single operator.
There additionally has developed a need for a portable screed which provides both compacting force as well as a smoothing force.
There is an additional need for a portable vibrating screed with an improved screed plate for smoothing an compacting operation.
There is yet a further need for a portable screed capable of selective adjustment to provide different ratios of consolidation to horizontal smoothing operation.